Why am I peeing?
In Binding of Isaac, I notice that I sometimes leave a little pee puddle upon entering a room. What's causing Isaac to urinate? Is it random or based on an item or effect I have at the moment?
It's a warning to remind you that your health is critical, i.e. that you only have half a Heart left.
As long as you're at half a regular Heart (regardless of how many Soul/Faith Hearts you have), you will soil yourself in terror each time you enter a room.
(If you're playing as ???, this will happen when your Faith is critical instead, because he has no regular health.)